[Path] Add GCode documentation of Path Workbench
[Path] Add GCode documentation of Path Workbench

This is a documentation of all GCodes used by the FreeCAD Path Workbench to e.g. simplify pre- and post-processor development.
Initial commit.

See [forum discussion](https://forum.freecadweb.org/viewtopic.php?f=15&t=42655).
Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master